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shmem: make shmem_inode_info::lock irq-safe
[GitHub/moto-9609/android_kernel_motorola_exynos9610.git] / mm / khugepaged.c
CommitLineData
b46e756f
KS		 1#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
2
3#include <linux/mm.h>
4#include <linux/sched.h>
5#include <linux/mmu_notifier.h>
6#include <linux/rmap.h>
7#include <linux/swap.h>
8#include <linux/mm_inline.h>
9#include <linux/kthread.h>
10#include <linux/khugepaged.h>
11#include <linux/freezer.h>
12#include <linux/mman.h>
13#include <linux/hashtable.h>
14#include <linux/userfaultfd_k.h>
15#include <linux/page_idle.h>
16#include <linux/swapops.h>
17
18#include <asm/tlb.h>
19#include <asm/pgalloc.h>
20#include "internal.h"
21
22enum scan_result {
23 SCAN_FAIL,
24 SCAN_SUCCEED,
25 SCAN_PMD_NULL,
26 SCAN_EXCEED_NONE_PTE,
27 SCAN_PTE_NON_PRESENT,
28 SCAN_PAGE_RO,
29 SCAN_NO_REFERENCED_PAGE,
30 SCAN_PAGE_NULL,
31 SCAN_SCAN_ABORT,
32 SCAN_PAGE_COUNT,
33 SCAN_PAGE_LRU,
34 SCAN_PAGE_LOCK,
35 SCAN_PAGE_ANON,
36 SCAN_PAGE_COMPOUND,
37 SCAN_ANY_PROCESS,
38 SCAN_VMA_NULL,
39 SCAN_VMA_CHECK,
40 SCAN_ADDRESS_RANGE,
41 SCAN_SWAP_CACHE_PAGE,
42 SCAN_DEL_PAGE_LRU,
43 SCAN_ALLOC_HUGE_PAGE_FAIL,
44 SCAN_CGROUP_CHARGE_FAIL,
45 SCAN_EXCEED_SWAP_PTE
46};
47
48#define CREATE_TRACE_POINTS
49#include <trace/events/huge_memory.h>
50
51/* default scan 8*512 pte (or vmas) every 30 second */
52static unsigned int khugepaged_pages_to_scan __read_mostly;
53static unsigned int khugepaged_pages_collapsed;
54static unsigned int khugepaged_full_scans;
55static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
56/* during fragmentation poll the hugepage allocator once every minute */
57static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
58static unsigned long khugepaged_sleep_expire;
59static DEFINE_SPINLOCK(khugepaged_mm_lock);
60static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
61/*
62 * default collapse hugepages if there is at least one pte mapped like
63 * it would have happened if the vma was large enough during page
64 * fault.
65 */
66static unsigned int khugepaged_max_ptes_none __read_mostly;
67static unsigned int khugepaged_max_ptes_swap __read_mostly;
68
69#define MM_SLOTS_HASH_BITS 10
70static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS);
71
72static struct kmem_cache *mm_slot_cache __read_mostly;
73
74/**
75 * struct mm_slot - hash lookup from mm to mm_slot
76 * @hash: hash collision list
77 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
78 * @mm: the mm that this information is valid for
79 */
80struct mm_slot {
81 struct hlist_node hash;
82 struct list_head mm_node;
83 struct mm_struct *mm;
84};
85
86/**
87 * struct khugepaged_scan - cursor for scanning
88 * @mm_head: the head of the mm list to scan
89 * @mm_slot: the current mm_slot we are scanning
90 * @address: the next address inside that to be scanned
91 *
92 * There is only the one khugepaged_scan instance of this cursor structure.
93 */
94struct khugepaged_scan {
95 struct list_head mm_head;
96 struct mm_slot *mm_slot;
97 unsigned long address;
98};
99
100static struct khugepaged_scan khugepaged_scan = {
101 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
102};
103
104static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
105 struct kobj_attribute *attr,
106 char *buf)
107{
108 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
109}
110
111static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
112 struct kobj_attribute *attr,
113 const char *buf, size_t count)
114{
115 unsigned long msecs;
116 int err;
117
118 err = kstrtoul(buf, 10, &msecs);
119 if (err || msecs > UINT_MAX)
120 return -EINVAL;
121
122 khugepaged_scan_sleep_millisecs = msecs;
123 khugepaged_sleep_expire = 0;
124 wake_up_interruptible(&khugepaged_wait);
125
126 return count;
127}
128static struct kobj_attribute scan_sleep_millisecs_attr =
129 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
130 scan_sleep_millisecs_store);
131
132static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
133 struct kobj_attribute *attr,
134 char *buf)
135{
136 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
137}
138
139static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
140 struct kobj_attribute *attr,
141 const char *buf, size_t count)
142{
143 unsigned long msecs;
144 int err;
145
146 err = kstrtoul(buf, 10, &msecs);
147 if (err || msecs > UINT_MAX)
148 return -EINVAL;
149
150 khugepaged_alloc_sleep_millisecs = msecs;
151 khugepaged_sleep_expire = 0;
152 wake_up_interruptible(&khugepaged_wait);
153
154 return count;
155}
156static struct kobj_attribute alloc_sleep_millisecs_attr =
157 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
158 alloc_sleep_millisecs_store);
159
160static ssize_t pages_to_scan_show(struct kobject *kobj,
161 struct kobj_attribute *attr,
162 char *buf)
163{
164 return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
165}
166static ssize_t pages_to_scan_store(struct kobject *kobj,
167 struct kobj_attribute *attr,
168 const char *buf, size_t count)
169{
170 int err;
171 unsigned long pages;
172
173 err = kstrtoul(buf, 10, &pages);
174 if (err || !pages || pages > UINT_MAX)
175 return -EINVAL;
176
177 khugepaged_pages_to_scan = pages;
178
179 return count;
180}
181static struct kobj_attribute pages_to_scan_attr =
182 __ATTR(pages_to_scan, 0644, pages_to_scan_show,
183 pages_to_scan_store);
184
185static ssize_t pages_collapsed_show(struct kobject *kobj,
186 struct kobj_attribute *attr,
187 char *buf)
188{
189 return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
190}
191static struct kobj_attribute pages_collapsed_attr =
192 __ATTR_RO(pages_collapsed);
193
194static ssize_t full_scans_show(struct kobject *kobj,
195 struct kobj_attribute *attr,
196 char *buf)
197{
198 return sprintf(buf, "%u\n", khugepaged_full_scans);
199}
200static struct kobj_attribute full_scans_attr =
201 __ATTR_RO(full_scans);
202
203static ssize_t khugepaged_defrag_show(struct kobject *kobj,
204 struct kobj_attribute *attr, char *buf)
205{
206 return single_hugepage_flag_show(kobj, attr, buf,
207 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
208}
209static ssize_t khugepaged_defrag_store(struct kobject *kobj,
210 struct kobj_attribute *attr,
211 const char *buf, size_t count)
212{
213 return single_hugepage_flag_store(kobj, attr, buf, count,
214 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
215}
216static struct kobj_attribute khugepaged_defrag_attr =
217 __ATTR(defrag, 0644, khugepaged_defrag_show,
218 khugepaged_defrag_store);
219
220/*
221 * max_ptes_none controls if khugepaged should collapse hugepages over
222 * any unmapped ptes in turn potentially increasing the memory
223 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
224 * reduce the available free memory in the system as it
225 * runs. Increasing max_ptes_none will instead potentially reduce the
226 * free memory in the system during the khugepaged scan.
227 */
228static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
229 struct kobj_attribute *attr,
230 char *buf)
231{
232 return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
233}
234static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
235 struct kobj_attribute *attr,
236 const char *buf, size_t count)
237{
238 int err;
239 unsigned long max_ptes_none;
240
241 err = kstrtoul(buf, 10, &max_ptes_none);
242 if (err || max_ptes_none > HPAGE_PMD_NR-1)
243 return -EINVAL;
244
245 khugepaged_max_ptes_none = max_ptes_none;
246
247 return count;
248}
249static struct kobj_attribute khugepaged_max_ptes_none_attr =
250 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
251 khugepaged_max_ptes_none_store);
252
253static ssize_t khugepaged_max_ptes_swap_show(struct kobject *kobj,
254 struct kobj_attribute *attr,
255 char *buf)
256{
257 return sprintf(buf, "%u\n", khugepaged_max_ptes_swap);
258}
259
260static ssize_t khugepaged_max_ptes_swap_store(struct kobject *kobj,
261 struct kobj_attribute *attr,
262 const char *buf, size_t count)
263{
264 int err;
265 unsigned long max_ptes_swap;
266
267 err = kstrtoul(buf, 10, &max_ptes_swap);
268 if (err || max_ptes_swap > HPAGE_PMD_NR-1)
269 return -EINVAL;
270
271 khugepaged_max_ptes_swap = max_ptes_swap;
272
273 return count;
274}
275
276static struct kobj_attribute khugepaged_max_ptes_swap_attr =
277 __ATTR(max_ptes_swap, 0644, khugepaged_max_ptes_swap_show,
278 khugepaged_max_ptes_swap_store);
279
280static struct attribute *khugepaged_attr[] = {
281 &khugepaged_defrag_attr.attr,
282 &khugepaged_max_ptes_none_attr.attr,
283 &pages_to_scan_attr.attr,
284 &pages_collapsed_attr.attr,
285 &full_scans_attr.attr,
286 &scan_sleep_millisecs_attr.attr,
287 &alloc_sleep_millisecs_attr.attr,
288 &khugepaged_max_ptes_swap_attr.attr,
289 NULL,
290};
291
292struct attribute_group khugepaged_attr_group = {
293 .attrs = khugepaged_attr,
294 .name = "khugepaged",
295};
296
297#define VM_NO_KHUGEPAGED (VM_SPECIAL | VM_HUGETLB | VM_SHARED | VM_MAYSHARE)
298
299int hugepage_madvise(struct vm_area_struct *vma,
300 unsigned long *vm_flags, int advice)
301{
302 switch (advice) {
303 case MADV_HUGEPAGE:
304#ifdef CONFIG_S390
305 /*
306 * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390
307 * can't handle this properly after s390_enable_sie, so we simply
308 * ignore the madvise to prevent qemu from causing a SIGSEGV.
309 */
310 if (mm_has_pgste(vma->vm_mm))
311 return 0;
312#endif
313 *vm_flags &= ~VM_NOHUGEPAGE;
314 *vm_flags |= VM_HUGEPAGE;
315 /*
316 * If the vma become good for khugepaged to scan,
317 * register it here without waiting a page fault that
318 * may not happen any time soon.
319 */
320 if (!(*vm_flags & VM_NO_KHUGEPAGED) &&
321 khugepaged_enter_vma_merge(vma, *vm_flags))
322 return -ENOMEM;
323 break;
324 case MADV_NOHUGEPAGE:
325 *vm_flags &= ~VM_HUGEPAGE;
326 *vm_flags |= VM_NOHUGEPAGE;
327 /*
328 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
329 * this vma even if we leave the mm registered in khugepaged if
330 * it got registered before VM_NOHUGEPAGE was set.
331 */
332 break;
333 }
334
335 return 0;
336}
337
338int __init khugepaged_init(void)
339{
340 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
341 sizeof(struct mm_slot),
342 __alignof__(struct mm_slot), 0, NULL);
343 if (!mm_slot_cache)
344 return -ENOMEM;
345
346 khugepaged_pages_to_scan = HPAGE_PMD_NR * 8;
347 khugepaged_max_ptes_none = HPAGE_PMD_NR - 1;
348 khugepaged_max_ptes_swap = HPAGE_PMD_NR / 8;
349
350 return 0;
351}
352
353void __init khugepaged_destroy(void)
354{
355 kmem_cache_destroy(mm_slot_cache);
356}
357
358static inline struct mm_slot *alloc_mm_slot(void)
359{
360 if (!mm_slot_cache) /* initialization failed */
361 return NULL;
362 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
363}
364
365static inline void free_mm_slot(struct mm_slot *mm_slot)
366{
367 kmem_cache_free(mm_slot_cache, mm_slot);
368}
369
370static struct mm_slot *get_mm_slot(struct mm_struct *mm)
371{
372 struct mm_slot *mm_slot;
373
374 hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm)
375 if (mm == mm_slot->mm)
376 return mm_slot;
377
378 return NULL;
379}
380
381static void insert_to_mm_slots_hash(struct mm_struct *mm,
382 struct mm_slot *mm_slot)
383{
384 mm_slot->mm = mm;
385 hash_add(mm_slots_hash, &mm_slot->hash, (long)mm);
386}
387
388static inline int khugepaged_test_exit(struct mm_struct *mm)
389{
390 return atomic_read(&mm->mm_users) == 0;
391}
392
393int __khugepaged_enter(struct mm_struct *mm)
394{
395 struct mm_slot *mm_slot;
396 int wakeup;
397
398 mm_slot = alloc_mm_slot();
399 if (!mm_slot)
400 return -ENOMEM;
401
402 /* __khugepaged_exit() must not run from under us */
403 VM_BUG_ON_MM(khugepaged_test_exit(mm), mm);
404 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
405 free_mm_slot(mm_slot);
406 return 0;
407 }
408
409 spin_lock(&khugepaged_mm_lock);
410 insert_to_mm_slots_hash(mm, mm_slot);
411 /*
412 * Insert just behind the scanning cursor, to let the area settle
413 * down a little.
414 */
415 wakeup = list_empty(&khugepaged_scan.mm_head);
416 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
417 spin_unlock(&khugepaged_mm_lock);
418
419 atomic_inc(&mm->mm_count);
420 if (wakeup)
421 wake_up_interruptible(&khugepaged_wait);
422
423 return 0;
424}
425
426int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
427 unsigned long vm_flags)
428{
429 unsigned long hstart, hend;
430 if (!vma->anon_vma)
431 /*
432 * Not yet faulted in so we will register later in the
433 * page fault if needed.
434 */
435 return 0;
436 if (vma->vm_ops || (vm_flags & VM_NO_KHUGEPAGED))
437 /* khugepaged not yet working on file or special mappings */
438 return 0;
439 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
440 hend = vma->vm_end & HPAGE_PMD_MASK;
441 if (hstart < hend)
442 return khugepaged_enter(vma, vm_flags);
443 return 0;
444}
445
446void __khugepaged_exit(struct mm_struct *mm)
447{
448 struct mm_slot *mm_slot;
449 int free = 0;
450
451 spin_lock(&khugepaged_mm_lock);
452 mm_slot = get_mm_slot(mm);
453 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
454 hash_del(&mm_slot->hash);
455 list_del(&mm_slot->mm_node);
456 free = 1;
457 }
458 spin_unlock(&khugepaged_mm_lock);
459
460 if (free) {
461 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
462 free_mm_slot(mm_slot);
463 mmdrop(mm);
464 } else if (mm_slot) {
465 /*
466 * This is required to serialize against
467 * khugepaged_test_exit() (which is guaranteed to run
468 * under mmap sem read mode). Stop here (after we
469 * return all pagetables will be destroyed) until
470 * khugepaged has finished working on the pagetables
471 * under the mmap_sem.
472 */
473 down_write(&mm->mmap_sem);
474 up_write(&mm->mmap_sem);
475 }
476}
477
478static void release_pte_page(struct page *page)
479{
480 /* 0 stands for page_is_file_cache(page) == false */
481 dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
482 unlock_page(page);
483 putback_lru_page(page);
484}
485
486static void release_pte_pages(pte_t *pte, pte_t *_pte)
487{
488 while (--_pte >= pte) {
489 pte_t pteval = *_pte;
490 if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval)))
491 release_pte_page(pte_page(pteval));
492 }
493}
494
495static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
496 unsigned long address,
497 pte_t *pte)
498{
499 struct page *page = NULL;
500 pte_t *_pte;
501 int none_or_zero = 0, result = 0;
502 bool referenced = false, writable = false;
503
504 for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
505 _pte++, address += PAGE_SIZE) {
506 pte_t pteval = *_pte;
507 if (pte_none(pteval) || (pte_present(pteval) &&
508 is_zero_pfn(pte_pfn(pteval)))) {
509 if (!userfaultfd_armed(vma) &&
510 ++none_or_zero <= khugepaged_max_ptes_none) {
511 continue;
512 } else {
513 result = SCAN_EXCEED_NONE_PTE;
514 goto out;
515 }
516 }
517 if (!pte_present(pteval)) {
518 result = SCAN_PTE_NON_PRESENT;
519 goto out;
520 }
521 page = vm_normal_page(vma, address, pteval);
522 if (unlikely(!page)) {
523 result = SCAN_PAGE_NULL;
524 goto out;
525 }
526
527 VM_BUG_ON_PAGE(PageCompound(page), page);
528 VM_BUG_ON_PAGE(!PageAnon(page), page);
529 VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
530
531 /*
532 * We can do it before isolate_lru_page because the
533 * page can't be freed from under us. NOTE: PG_lock
534 * is needed to serialize against split_huge_page
535 * when invoked from the VM.
536 */
537 if (!trylock_page(page)) {
538 result = SCAN_PAGE_LOCK;
539 goto out;
540 }
541
542 /*
543 * cannot use mapcount: can't collapse if there's a gup pin.
544 * The page must only be referenced by the scanned process
545 * and page swap cache.
546 */
547 if (page_count(page) != 1 + !!PageSwapCache(page)) {
548 unlock_page(page);
549 result = SCAN_PAGE_COUNT;
550 goto out;
551 }
552 if (pte_write(pteval)) {
553 writable = true;
554 } else {
555 if (PageSwapCache(page) &&
556 !reuse_swap_page(page, NULL)) {
557 unlock_page(page);
558 result = SCAN_SWAP_CACHE_PAGE;
559 goto out;
560 }
561 /*
562 * Page is not in the swap cache. It can be collapsed
563 * into a THP.
564 */
565 }
566
567 /*
568 * Isolate the page to avoid collapsing an hugepage
569 * currently in use by the VM.
570 */
571 if (isolate_lru_page(page)) {
572 unlock_page(page);
573 result = SCAN_DEL_PAGE_LRU;
574 goto out;
575 }
576 /* 0 stands for page_is_file_cache(page) == false */
577 inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
578 VM_BUG_ON_PAGE(!PageLocked(page), page);
579 VM_BUG_ON_PAGE(PageLRU(page), page);
580
581 /* If there is no mapped pte young don't collapse the page */
582 if (pte_young(pteval) ||
583 page_is_young(page) || PageReferenced(page) ||
584 mmu_notifier_test_young(vma->vm_mm, address))
585 referenced = true;
586 }
587 if (likely(writable)) {
588 if (likely(referenced)) {
589 result = SCAN_SUCCEED;
590 trace_mm_collapse_huge_page_isolate(page, none_or_zero,
591 referenced, writable, result);
592 return 1;
593 }
594 } else {
595 result = SCAN_PAGE_RO;
596 }
597
598out:
599 release_pte_pages(pte, _pte);
600 trace_mm_collapse_huge_page_isolate(page, none_or_zero,
601 referenced, writable, result);
602 return 0;
603}
604
605static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
606 struct vm_area_struct *vma,
607 unsigned long address,
608 spinlock_t *ptl)
609{
610 pte_t *_pte;
611 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
612 pte_t pteval = *_pte;
613 struct page *src_page;
614
615 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
616 clear_user_highpage(page, address);
617 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
618 if (is_zero_pfn(pte_pfn(pteval))) {
619 /*
620 * ptl mostly unnecessary.
621 */
622 spin_lock(ptl);
623 /*
624 * paravirt calls inside pte_clear here are
625 * superfluous.
626 */
627 pte_clear(vma->vm_mm, address, _pte);
628 spin_unlock(ptl);
629 }
630 } else {
631 src_page = pte_page(pteval);
632 copy_user_highpage(page, src_page, address, vma);
633 VM_BUG_ON_PAGE(page_mapcount(src_page) != 1, src_page);
634 release_pte_page(src_page);
635 /*
636 * ptl mostly unnecessary, but preempt has to
637 * be disabled to update the per-cpu stats
638 * inside page_remove_rmap().
639 */
640 spin_lock(ptl);
641 /*
642 * paravirt calls inside pte_clear here are
643 * superfluous.
644 */
645 pte_clear(vma->vm_mm, address, _pte);
646 page_remove_rmap(src_page, false);
647 spin_unlock(ptl);
648 free_page_and_swap_cache(src_page);
649 }
650
651 address += PAGE_SIZE;
652 page++;
653 }
654}
655
656static void khugepaged_alloc_sleep(void)
657{
658 DEFINE_WAIT(wait);
659
660 add_wait_queue(&khugepaged_wait, &wait);
661 freezable_schedule_timeout_interruptible(
662 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
663 remove_wait_queue(&khugepaged_wait, &wait);
664}
665
666static int khugepaged_node_load[MAX_NUMNODES];
667
668static bool khugepaged_scan_abort(int nid)
669{
670 int i;
671
672 /*
673 * If zone_reclaim_mode is disabled, then no extra effort is made to
674 * allocate memory locally.
675 */
676 if (!zone_reclaim_mode)
677 return false;
678
679 /* If there is a count for this node already, it must be acceptable */
680 if (khugepaged_node_load[nid])
681 return false;
682
683 for (i = 0; i < MAX_NUMNODES; i++) {
684 if (!khugepaged_node_load[i])
685 continue;
686 if (node_distance(nid, i) > RECLAIM_DISTANCE)
687 return true;
688 }
689 return false;
690}
691
692/* Defrag for khugepaged will enter direct reclaim/compaction if necessary */
693static inline gfp_t alloc_hugepage_khugepaged_gfpmask(void)
694{
695 return GFP_TRANSHUGE | (khugepaged_defrag() ? __GFP_DIRECT_RECLAIM : 0);
696}
697
698#ifdef CONFIG_NUMA
699static int khugepaged_find_target_node(void)
700{
701 static int last_khugepaged_target_node = NUMA_NO_NODE;
702 int nid, target_node = 0, max_value = 0;
703
704 /* find first node with max normal pages hit */
705 for (nid = 0; nid < MAX_NUMNODES; nid++)
706 if (khugepaged_node_load[nid] > max_value) {
707 max_value = khugepaged_node_load[nid];
708 target_node = nid;
709 }
710
711 /* do some balance if several nodes have the same hit record */
712 if (target_node <= last_khugepaged_target_node)
713 for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES;
714 nid++)
715 if (max_value == khugepaged_node_load[nid]) {
716 target_node = nid;
717 break;
718 }
719
720 last_khugepaged_target_node = target_node;
721 return target_node;
722}
723
724static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
725{
726 if (IS_ERR(*hpage)) {
727 if (!*wait)
728 return false;
729
730 *wait = false;
731 *hpage = NULL;
732 khugepaged_alloc_sleep();
733 } else if (*hpage) {
734 put_page(*hpage);
735 *hpage = NULL;
736 }
737
738 return true;
739}
740
741static struct page *
988ddb71 742khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node)
b46e756f
KS		 743{
744 VM_BUG_ON_PAGE(*hpage, *hpage);
745
b46e756f
KS		 746 *hpage = __alloc_pages_node(node, gfp, HPAGE_PMD_ORDER);
747 if (unlikely(!*hpage)) {
748 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
749 *hpage = ERR_PTR(-ENOMEM);
750 return NULL;
751 }
752
753 prep_transhuge_page(*hpage);
754 count_vm_event(THP_COLLAPSE_ALLOC);
755 return *hpage;
756}
757#else
758static int khugepaged_find_target_node(void)
759{
760 return 0;
761}
762
763static inline struct page *alloc_khugepaged_hugepage(void)
764{
765 struct page *page;
766
767 page = alloc_pages(alloc_hugepage_khugepaged_gfpmask(),
768 HPAGE_PMD_ORDER);
769 if (page)
770 prep_transhuge_page(page);
771 return page;
772}
773
774static struct page *khugepaged_alloc_hugepage(bool *wait)
775{
776 struct page *hpage;
777
778 do {
779 hpage = alloc_khugepaged_hugepage();
780 if (!hpage) {
781 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
782 if (!*wait)
783 return NULL;
784
785 *wait = false;
786 khugepaged_alloc_sleep();
787 } else
788 count_vm_event(THP_COLLAPSE_ALLOC);
789 } while (unlikely(!hpage) && likely(khugepaged_enabled()));
790
791 return hpage;
792}
793
794static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
795{
796 if (!*hpage)
797 *hpage = khugepaged_alloc_hugepage(wait);
798
799 if (unlikely(!*hpage))
800 return false;
801
802 return true;
803}
804
805static struct page *
988ddb71 806khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node)
b46e756f 807{
b46e756f
KS		 808 VM_BUG_ON(!*hpage);
809
810 return *hpage;
811}
812#endif
813
814static bool hugepage_vma_check(struct vm_area_struct *vma)
815{
816 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
817 (vma->vm_flags & VM_NOHUGEPAGE))
818 return false;
819 if (!vma->anon_vma || vma->vm_ops)
820 return false;
821 if (is_vma_temporary_stack(vma))
822 return false;
823 return !(vma->vm_flags & VM_NO_KHUGEPAGED);
824}
825
826/*
827 * If mmap_sem temporarily dropped, revalidate vma
828 * before taking mmap_sem.
829 * Return 0 if succeeds, otherwise return none-zero
830 * value (scan code).
831 */
832
833static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address)
834{
835 struct vm_area_struct *vma;
836 unsigned long hstart, hend;
837
838 if (unlikely(khugepaged_test_exit(mm)))
839 return SCAN_ANY_PROCESS;
840
841 vma = find_vma(mm, address);
842 if (!vma)
843 return SCAN_VMA_NULL;
844
845 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
846 hend = vma->vm_end & HPAGE_PMD_MASK;
847 if (address < hstart || address + HPAGE_PMD_SIZE > hend)
848 return SCAN_ADDRESS_RANGE;
849 if (!hugepage_vma_check(vma))
850 return SCAN_VMA_CHECK;
851 return 0;
852}
853
854/*
855 * Bring missing pages in from swap, to complete THP collapse.
856 * Only done if khugepaged_scan_pmd believes it is worthwhile.
857 *
858 * Called and returns without pte mapped or spinlocks held,
859 * but with mmap_sem held to protect against vma changes.
860 */
861
862static bool __collapse_huge_page_swapin(struct mm_struct *mm,
863 struct vm_area_struct *vma,
864 unsigned long address, pmd_t *pmd)
865{
866 pte_t pteval;
867 int swapped_in = 0, ret = 0;
868 struct fault_env fe = {
869 .vma = vma,
870 .address = address,
871 .flags = FAULT_FLAG_ALLOW_RETRY,
872 .pmd = pmd,
873 };
874
875 fe.pte = pte_offset_map(pmd, address);
876 for (; fe.address < address + HPAGE_PMD_NR*PAGE_SIZE;
877 fe.pte++, fe.address += PAGE_SIZE) {
878 pteval = *fe.pte;
879 if (!is_swap_pte(pteval))
880 continue;
881 swapped_in++;
882 ret = do_swap_page(&fe, pteval);
883 /* do_swap_page returns VM_FAULT_RETRY with released mmap_sem */
884 if (ret & VM_FAULT_RETRY) {
885 down_read(&mm->mmap_sem);
886 /* vma is no longer available, don't continue to swapin */
887 if (hugepage_vma_revalidate(mm, address))
888 return false;
889 /* check if the pmd is still valid */
890 if (mm_find_pmd(mm, address) != pmd)
891 return false;
892 }
893 if (ret & VM_FAULT_ERROR) {
894 trace_mm_collapse_huge_page_swapin(mm, swapped_in, 0);
895 return false;
896 }
897 /* pte is unmapped now, we need to map it */
898 fe.pte = pte_offset_map(pmd, fe.address);
899 }
900 fe.pte--;
901 pte_unmap(fe.pte);
902 trace_mm_collapse_huge_page_swapin(mm, swapped_in, 1);
903 return true;
904}
905
906static void collapse_huge_page(struct mm_struct *mm,
907 unsigned long address,
908 struct page **hpage,
909 struct vm_area_struct *vma,
910 int node)
911{
912 pmd_t *pmd, _pmd;
913 pte_t *pte;
914 pgtable_t pgtable;
915 struct page *new_page;
916 spinlock_t *pmd_ptl, *pte_ptl;
917 int isolated = 0, result = 0;
918 struct mem_cgroup *memcg;
919 unsigned long mmun_start; /* For mmu_notifiers */
920 unsigned long mmun_end; /* For mmu_notifiers */
921 gfp_t gfp;
922
923 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
924
925 /* Only allocate from the target node */
926 gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_OTHER_NODE | __GFP_THISNODE;
927
988ddb71
KS		 928 /*
929 * Before allocating the hugepage, release the mmap_sem read lock.
930 * The allocation can take potentially a long time if it involves
931 * sync compaction, and we do not need to hold the mmap_sem during
932 * that. We will recheck the vma after taking it again in write mode.
933 */
934 up_read(&mm->mmap_sem);
935 new_page = khugepaged_alloc_page(hpage, gfp, node);
b46e756f
KS		 936 if (!new_page) {
937 result = SCAN_ALLOC_HUGE_PAGE_FAIL;
938 goto out_nolock;
939 }
940
941 if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) {
942 result = SCAN_CGROUP_CHARGE_FAIL;
943 goto out_nolock;
944 }
945
946 down_read(&mm->mmap_sem);
947 result = hugepage_vma_revalidate(mm, address);
948 if (result) {
949 mem_cgroup_cancel_charge(new_page, memcg, true);
950 up_read(&mm->mmap_sem);
951 goto out_nolock;
952 }
953
954 pmd = mm_find_pmd(mm, address);
955 if (!pmd) {
956 result = SCAN_PMD_NULL;
957 mem_cgroup_cancel_charge(new_page, memcg, true);
958 up_read(&mm->mmap_sem);
959 goto out_nolock;
960 }
961
962 /*
963 * __collapse_huge_page_swapin always returns with mmap_sem locked.
964 * If it fails, release mmap_sem and jump directly out.
965 * Continuing to collapse causes inconsistency.
966 */
967 if (!__collapse_huge_page_swapin(mm, vma, address, pmd)) {
968 mem_cgroup_cancel_charge(new_page, memcg, true);
969 up_read(&mm->mmap_sem);
970 goto out_nolock;
971 }
972
973 up_read(&mm->mmap_sem);
974 /*
975 * Prevent all access to pagetables with the exception of
976 * gup_fast later handled by the ptep_clear_flush and the VM
977 * handled by the anon_vma lock + PG_lock.
978 */
979 down_write(&mm->mmap_sem);
980 result = hugepage_vma_revalidate(mm, address);
981 if (result)
982 goto out;
983 /* check if the pmd is still valid */
984 if (mm_find_pmd(mm, address) != pmd)
985 goto out;
986
987 anon_vma_lock_write(vma->anon_vma);
988
989 pte = pte_offset_map(pmd, address);
990 pte_ptl = pte_lockptr(mm, pmd);
991
992 mmun_start = address;
993 mmun_end = address + HPAGE_PMD_SIZE;
994 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
995 pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */
996 /*
997 * After this gup_fast can't run anymore. This also removes
998 * any huge TLB entry from the CPU so we won't allow
999 * huge and small TLB entries for the same virtual address
1000 * to avoid the risk of CPU bugs in that area.
1001 */
1002 _pmd = pmdp_collapse_flush(vma, address, pmd);
1003 spin_unlock(pmd_ptl);
1004 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1005
1006 spin_lock(pte_ptl);
1007 isolated = __collapse_huge_page_isolate(vma, address, pte);
1008 spin_unlock(pte_ptl);
1009
1010 if (unlikely(!isolated)) {
1011 pte_unmap(pte);
1012 spin_lock(pmd_ptl);
1013 BUG_ON(!pmd_none(*pmd));
1014 /*
1015 * We can only use set_pmd_at when establishing
1016 * hugepmds and never for establishing regular pmds that
1017 * points to regular pagetables. Use pmd_populate for that
1018 */
1019 pmd_populate(mm, pmd, pmd_pgtable(_pmd));
1020 spin_unlock(pmd_ptl);
1021 anon_vma_unlock_write(vma->anon_vma);
1022 result = SCAN_FAIL;
1023 goto out;
1024 }
1025
1026 /*
1027 * All pages are isolated and locked so anon_vma rmap
1028 * can't run anymore.
1029 */
1030 anon_vma_unlock_write(vma->anon_vma);
1031
1032 __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl);
1033 pte_unmap(pte);
1034 __SetPageUptodate(new_page);
1035 pgtable = pmd_pgtable(_pmd);
1036
1037 _pmd = mk_huge_pmd(new_page, vma->vm_page_prot);
1038 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
1039
1040 /*
1041 * spin_lock() below is not the equivalent of smp_wmb(), so
1042 * this is needed to avoid the copy_huge_page writes to become
1043 * visible after the set_pmd_at() write.
1044 */
1045 smp_wmb();
1046
1047 spin_lock(pmd_ptl);
1048 BUG_ON(!pmd_none(*pmd));
1049 page_add_new_anon_rmap(new_page, vma, address, true);
1050 mem_cgroup_commit_charge(new_page, memcg, false, true);
1051 lru_cache_add_active_or_unevictable(new_page, vma);
1052 pgtable_trans_huge_deposit(mm, pmd, pgtable);
1053 set_pmd_at(mm, address, pmd, _pmd);
1054 update_mmu_cache_pmd(vma, address, pmd);
1055 spin_unlock(pmd_ptl);
1056
1057 *hpage = NULL;
1058
1059 khugepaged_pages_collapsed++;
1060 result = SCAN_SUCCEED;
1061out_up_write:
1062 up_write(&mm->mmap_sem);
1063out_nolock:
1064 trace_mm_collapse_huge_page(mm, isolated, result);
1065 return;
1066out:
1067 mem_cgroup_cancel_charge(new_page, memcg, true);
1068 goto out_up_write;
1069}
1070
1071static int khugepaged_scan_pmd(struct mm_struct *mm,
1072 struct vm_area_struct *vma,
1073 unsigned long address,
1074 struct page **hpage)
1075{
1076 pmd_t *pmd;
1077 pte_t *pte, *_pte;
1078 int ret = 0, none_or_zero = 0, result = 0;
1079 struct page *page = NULL;
1080 unsigned long _address;
1081 spinlock_t *ptl;
1082 int node = NUMA_NO_NODE, unmapped = 0;
1083 bool writable = false, referenced = false;
1084
1085 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1086
1087 pmd = mm_find_pmd(mm, address);
1088 if (!pmd) {
1089 result = SCAN_PMD_NULL;
1090 goto out;
1091 }
1092
1093 memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load));
1094 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
1095 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
1096 _pte++, _address += PAGE_SIZE) {
1097 pte_t pteval = *_pte;
1098 if (is_swap_pte(pteval)) {
1099 if (++unmapped <= khugepaged_max_ptes_swap) {
1100 continue;
1101 } else {
1102 result = SCAN_EXCEED_SWAP_PTE;
1103 goto out_unmap;
1104 }
1105 }
1106 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
1107 if (!userfaultfd_armed(vma) &&
1108 ++none_or_zero <= khugepaged_max_ptes_none) {
1109 continue;
1110 } else {
1111 result = SCAN_EXCEED_NONE_PTE;
1112 goto out_unmap;
1113 }
1114 }
1115 if (!pte_present(pteval)) {
1116 result = SCAN_PTE_NON_PRESENT;
1117 goto out_unmap;
1118 }
1119 if (pte_write(pteval))
1120 writable = true;
1121
1122 page = vm_normal_page(vma, _address, pteval);
1123 if (unlikely(!page)) {
1124 result = SCAN_PAGE_NULL;
1125 goto out_unmap;
1126 }
1127
1128 /* TODO: teach khugepaged to collapse THP mapped with pte */
1129 if (PageCompound(page)) {
1130 result = SCAN_PAGE_COMPOUND;
1131 goto out_unmap;
1132 }
1133
1134 /*
1135 * Record which node the original page is from and save this
1136 * information to khugepaged_node_load[].
1137 * Khupaged will allocate hugepage from the node has the max
1138 * hit record.
1139 */
1140 node = page_to_nid(page);
1141 if (khugepaged_scan_abort(node)) {
1142 result = SCAN_SCAN_ABORT;
1143 goto out_unmap;
1144 }
1145 khugepaged_node_load[node]++;
1146 if (!PageLRU(page)) {
1147 result = SCAN_PAGE_LRU;
1148 goto out_unmap;
1149 }
1150 if (PageLocked(page)) {
1151 result = SCAN_PAGE_LOCK;
1152 goto out_unmap;
1153 }
1154 if (!PageAnon(page)) {
1155 result = SCAN_PAGE_ANON;
1156 goto out_unmap;
1157 }
1158
1159 /*
1160 * cannot use mapcount: can't collapse if there's a gup pin.
1161 * The page must only be referenced by the scanned process
1162 * and page swap cache.
1163 */
1164 if (page_count(page) != 1 + !!PageSwapCache(page)) {
1165 result = SCAN_PAGE_COUNT;
1166 goto out_unmap;
1167 }
1168 if (pte_young(pteval) ||
1169 page_is_young(page) || PageReferenced(page) ||
1170 mmu_notifier_test_young(vma->vm_mm, address))
1171 referenced = true;
1172 }
1173 if (writable) {
1174 if (referenced) {
1175 result = SCAN_SUCCEED;
1176 ret = 1;
1177 } else {
1178 result = SCAN_NO_REFERENCED_PAGE;
1179 }
1180 } else {
1181 result = SCAN_PAGE_RO;
1182 }
1183out_unmap:
1184 pte_unmap_unlock(pte, ptl);
1185 if (ret) {
1186 node = khugepaged_find_target_node();
1187 /* collapse_huge_page will return with the mmap_sem released */
1188 collapse_huge_page(mm, address, hpage, vma, node);
1189 }
1190out:
1191 trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced,
1192 none_or_zero, result, unmapped);
1193 return ret;
1194}
1195
1196static void collect_mm_slot(struct mm_slot *mm_slot)
1197{
1198 struct mm_struct *mm = mm_slot->mm;
1199
1200 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
1201
1202 if (khugepaged_test_exit(mm)) {
1203 /* free mm_slot */
1204 hash_del(&mm_slot->hash);
1205 list_del(&mm_slot->mm_node);
1206
1207 /*
1208 * Not strictly needed because the mm exited already.
1209 *
1210 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1211 */
1212
1213 /* khugepaged_mm_lock actually not necessary for the below */
1214 free_mm_slot(mm_slot);
1215 mmdrop(mm);
1216 }
1217}
1218
1219static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
1220 struct page **hpage)
1221 __releases(&khugepaged_mm_lock)
1222 __acquires(&khugepaged_mm_lock)
1223{
1224 struct mm_slot *mm_slot;
1225 struct mm_struct *mm;
1226 struct vm_area_struct *vma;
1227 int progress = 0;
1228
1229 VM_BUG_ON(!pages);
1230 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
1231
1232 if (khugepaged_scan.mm_slot)
1233 mm_slot = khugepaged_scan.mm_slot;
1234 else {
1235 mm_slot = list_entry(khugepaged_scan.mm_head.next,
1236 struct mm_slot, mm_node);
1237 khugepaged_scan.address = 0;
1238 khugepaged_scan.mm_slot = mm_slot;
1239 }
1240 spin_unlock(&khugepaged_mm_lock);
1241
1242 mm = mm_slot->mm;
1243 down_read(&mm->mmap_sem);
1244 if (unlikely(khugepaged_test_exit(mm)))
1245 vma = NULL;
1246 else
1247 vma = find_vma(mm, khugepaged_scan.address);
1248
1249 progress++;
1250 for (; vma; vma = vma->vm_next) {
1251 unsigned long hstart, hend;
1252
1253 cond_resched();
1254 if (unlikely(khugepaged_test_exit(mm))) {
1255 progress++;
1256 break;
1257 }
1258 if (!hugepage_vma_check(vma)) {
1259skip:
1260 progress++;
1261 continue;
1262 }
1263 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1264 hend = vma->vm_end & HPAGE_PMD_MASK;
1265 if (hstart >= hend)
1266 goto skip;
1267 if (khugepaged_scan.address > hend)
1268 goto skip;
1269 if (khugepaged_scan.address < hstart)
1270 khugepaged_scan.address = hstart;
1271 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
1272
1273 while (khugepaged_scan.address < hend) {
1274 int ret;
1275 cond_resched();
1276 if (unlikely(khugepaged_test_exit(mm)))
1277 goto breakouterloop;
1278
1279 VM_BUG_ON(khugepaged_scan.address < hstart ||
1280 khugepaged_scan.address + HPAGE_PMD_SIZE >
1281 hend);
1282 ret = khugepaged_scan_pmd(mm, vma,
1283 khugepaged_scan.address,
1284 hpage);
1285 /* move to next address */
1286 khugepaged_scan.address += HPAGE_PMD_SIZE;
1287 progress += HPAGE_PMD_NR;
1288 if (ret)
1289 /* we released mmap_sem so break loop */
1290 goto breakouterloop_mmap_sem;
1291 if (progress >= pages)
1292 goto breakouterloop;
1293 }
1294 }
1295breakouterloop:
1296 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
1297breakouterloop_mmap_sem:
1298
1299 spin_lock(&khugepaged_mm_lock);
1300 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
1301 /*
1302 * Release the current mm_slot if this mm is about to die, or
1303 * if we scanned all vmas of this mm.
1304 */
1305 if (khugepaged_test_exit(mm) || !vma) {
1306 /*
1307 * Make sure that if mm_users is reaching zero while
1308 * khugepaged runs here, khugepaged_exit will find
1309 * mm_slot not pointing to the exiting mm.
1310 */
1311 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
1312 khugepaged_scan.mm_slot = list_entry(
1313 mm_slot->mm_node.next,
1314 struct mm_slot, mm_node);
1315 khugepaged_scan.address = 0;
1316 } else {
1317 khugepaged_scan.mm_slot = NULL;
1318 khugepaged_full_scans++;
1319 }
1320
1321 collect_mm_slot(mm_slot);
1322 }
1323
1324 return progress;
1325}
1326
1327static int khugepaged_has_work(void)
1328{
1329 return !list_empty(&khugepaged_scan.mm_head) &&
1330 khugepaged_enabled();
1331}
1332
1333static int khugepaged_wait_event(void)
1334{
1335 return !list_empty(&khugepaged_scan.mm_head) ||
1336 kthread_should_stop();
1337}
1338
1339static void khugepaged_do_scan(void)
1340{
1341 struct page *hpage = NULL;
1342 unsigned int progress = 0, pass_through_head = 0;
1343 unsigned int pages = khugepaged_pages_to_scan;
1344 bool wait = true;
1345
1346 barrier(); /* write khugepaged_pages_to_scan to local stack */
1347
1348 while (progress < pages) {
1349 if (!khugepaged_prealloc_page(&hpage, &wait))
1350 break;
1351
1352 cond_resched();
1353
1354 if (unlikely(kthread_should_stop() || try_to_freeze()))
1355 break;
1356
1357 spin_lock(&khugepaged_mm_lock);
1358 if (!khugepaged_scan.mm_slot)
1359 pass_through_head++;
1360 if (khugepaged_has_work() &&
1361 pass_through_head < 2)
1362 progress += khugepaged_scan_mm_slot(pages - progress,
1363 &hpage);
1364 else
1365 progress = pages;
1366 spin_unlock(&khugepaged_mm_lock);
1367 }
1368
1369 if (!IS_ERR_OR_NULL(hpage))
1370 put_page(hpage);
1371}
1372
1373static bool khugepaged_should_wakeup(void)
1374{
1375 return kthread_should_stop() ||
1376 time_after_eq(jiffies, khugepaged_sleep_expire);
1377}
1378
1379static void khugepaged_wait_work(void)
1380{
1381 if (khugepaged_has_work()) {
1382 const unsigned long scan_sleep_jiffies =
1383 msecs_to_jiffies(khugepaged_scan_sleep_millisecs);
1384
1385 if (!scan_sleep_jiffies)
1386 return;
1387
1388 khugepaged_sleep_expire = jiffies + scan_sleep_jiffies;
1389 wait_event_freezable_timeout(khugepaged_wait,
1390 khugepaged_should_wakeup(),
1391 scan_sleep_jiffies);
1392 return;
1393 }
1394
1395 if (khugepaged_enabled())
1396 wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
1397}
1398
1399static int khugepaged(void *none)
1400{
1401 struct mm_slot *mm_slot;
1402
1403 set_freezable();
1404 set_user_nice(current, MAX_NICE);
1405
1406 while (!kthread_should_stop()) {
1407 khugepaged_do_scan();
1408 khugepaged_wait_work();
1409 }
1410
1411 spin_lock(&khugepaged_mm_lock);
1412 mm_slot = khugepaged_scan.mm_slot;
1413 khugepaged_scan.mm_slot = NULL;
1414 if (mm_slot)
1415 collect_mm_slot(mm_slot);
1416 spin_unlock(&khugepaged_mm_lock);
1417 return 0;
1418}
1419
1420static void set_recommended_min_free_kbytes(void)
1421{
1422 struct zone *zone;
1423 int nr_zones = 0;
1424 unsigned long recommended_min;
1425
1426 for_each_populated_zone(zone)
1427 nr_zones++;
1428
1429 /* Ensure 2 pageblocks are free to assist fragmentation avoidance */
1430 recommended_min = pageblock_nr_pages * nr_zones * 2;
1431
1432 /*
1433 * Make sure that on average at least two pageblocks are almost free
1434 * of another type, one for a migratetype to fall back to and a
1435 * second to avoid subsequent fallbacks of other types There are 3
1436 * MIGRATE_TYPES we care about.
1437 */
1438 recommended_min += pageblock_nr_pages * nr_zones *
1439 MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;
1440
1441 /* don't ever allow to reserve more than 5% of the lowmem */
1442 recommended_min = min(recommended_min,
1443 (unsigned long) nr_free_buffer_pages() / 20);
1444 recommended_min <<= (PAGE_SHIFT-10);
1445
1446 if (recommended_min > min_free_kbytes) {
1447 if (user_min_free_kbytes >= 0)
1448 pr_info("raising min_free_kbytes from %d to %lu to help transparent hugepage allocations\n",
1449 min_free_kbytes, recommended_min);
1450
1451 min_free_kbytes = recommended_min;
1452 }
1453 setup_per_zone_wmarks();
1454}
1455
1456int start_stop_khugepaged(void)
1457{
1458 static struct task_struct *khugepaged_thread __read_mostly;
1459 static DEFINE_MUTEX(khugepaged_mutex);
1460 int err = 0;
1461
1462 mutex_lock(&khugepaged_mutex);
1463 if (khugepaged_enabled()) {
1464 if (!khugepaged_thread)
1465 khugepaged_thread = kthread_run(khugepaged, NULL,
1466 "khugepaged");
1467 if (IS_ERR(khugepaged_thread)) {
1468 pr_err("khugepaged: kthread_run(khugepaged) failed\n");
1469 err = PTR_ERR(khugepaged_thread);
1470 khugepaged_thread = NULL;
1471 goto fail;
1472 }
1473
1474 if (!list_empty(&khugepaged_scan.mm_head))
1475 wake_up_interruptible(&khugepaged_wait);
1476
1477 set_recommended_min_free_kbytes();
1478 } else if (khugepaged_thread) {
1479 kthread_stop(khugepaged_thread);
1480 khugepaged_thread = NULL;
1481 }
1482fail:
1483 mutex_unlock(&khugepaged_mutex);
1484 return err;
1485}